Liquid crystal display device having the same openings and manufacturing method thereof

ABSTRACT

An LCD device and a manufacturing method thereof having improved transmittance and contrast ratio are disclosed. 
     According to the LCD device and the manufacturing method thereof, a first common electrode which includes first and second horizontal electrode bars and a plurality of first vertical common electrode bars is disposed on a layer different from a second common electrode which includes a third horizontal common electrode bar and a plurality of second vertical common electrode bars. A pixel electrode which includes a horizontal pixel electrode bar and a plurality of vertical pixel electrode bars is disposed on the same layer as the second common electrode. The second common electrode is connected to the first common electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. 119 to Korean PatentApplication No. 10-2008-0121576, filed on Dec. 3, 2008, which is herebyincorporated by reference in its entirety.

BACKGROUND

1. Field of the Disclosure

This disclosure relates to a liquid crystal display device with improvedtransmittance and contrast ratio, and a driving method thereof.

2. Description of the Related Art

As the information society grows, flat display devices capable ofdisplaying information have been widely developed. These flat displaydevices include liquid crystal display (LCD) devices, organicelectro-luminescence display (OLED) devices, plasma display devices, andfield emission display devices. Among the above display devices, LCDdevices have the advantages that they are light and small and canprovide a low power drive and a full color scheme. Accordingly, LCDdevices have been widely used for mobile phones, navigation systems,portable computers, televisions and so on.

LCD devices control the transmittance of a liquid crystal on a liquidcrystal panel, thereby displaying a desired image. LCD devices generallyhave a poor viewing angle.

In order to improve the viewing angle, an LCD device with an in-planeswitching (IPS) mode has been proposed which generates a horizontalelectric field or an in-plane electric field by means of pixel electrodeand common electrode arranged on the same substrate. Also, the pixel andcommon electrodes included in the LCD device of the IPS mode have beendesigned to be arranged in one of several configurations, including aone-matal-one-ITO (1-metal-1-ITO), a two-ITO (2-1TO), and a 2MoTiconfiguration.

Among these electrode arrangement configurations, the 1-metal-1-ITOconfiguration includes common electrodes 103 a and 103 b and a pixelelectrode 107 arranged on different layers, as shown in FIG. 1. Thecommon electrodes 103 a and 103 b, which include a metal film, aredisposed on a substrate 101. Meanwhile, the pixel electrode 107, whichincludes a transparent conductive film such as an ITO film is disposedon a passivation (or protective) film 106.

The 1-metal-1-ITO configuration uses a mask in the formation of thecommon electrodes 103 a and 103 b. The mask can be aligned in anundesired position which is then shifted from a desired position to onedirection (for example, to the right side of the desired position)during the formation of the common electrodes 103 a and 103 b. In otherwords, a mask misalignment can be generated. In this case, shiftedcommon electrodes 105 a and 105 b may be formed. The shifted commonelectrodes 105 a and 105 b are separated in differing distances from thepixel electrode 107. More specifically, a first region A defined betweenthe first shifted common electrode 105 a and the pixel electrode 107 isof a width narrower than that of a second region B formed between thesecond shifted common electrode 105 b and the pixel electrode 107. Assuch, the transmittances of the first and second regions A and B withregards to the same voltage are different from each other, therebydeteriorating the overall (or general) transmittance as shown in FIG. 2.

The 2-ITO configuration includes a pixel electrode 113 and a commonelectrode 115 arranged on the same layer, i.e., on the surface of asubstrate 111, as shown in FIG. 3A. The pixel electrode 113 and thecommon electrode 115 are formed of the same material such as ITO.

In the 2-ITO configuration, an equipotential is formed on the pixelelectrode 113 and the common electrode 115. As such, a mean efficiencyof a liquid crystal positioned above the pixel electrode 113 and thecommon electrode 115 is decreased as shown in FIG. 3B. Likewise, thetransmittance of the pixel region is lowered. Therefore, the contrastratio is deteriorated.

Similarly, the 2MoTi configuration includes a pixel electrode 123 and acommon electrode 125 arranged on the same layer, i.e., on a substrate121, as shown in FIG. 4A. The pixel electrode 123 and the commonelectrode 125 are made of the same material such as MoTi.

As the pixel and common electrodes 123 and 125 made of MoTi are opaque,light can not penetrate through the pixel and common electrodes 123 and125, as shown in FIG. 4B. In other words, the aperture of the pixelregion is lowered. Accordingly, the light transmittance and brightnessare deteriorated.

BRIEF SUMMARY

Accordingly, the present embodiments are directed to an LCD device thatsubstantially obviates one or more of problems due to the limitationsand disadvantages of the related art, and a manufacturing methodthereof.

An object of the present embodiment is to provide an LCD device capableof improving both its transmittance and contrast ratio, and amanufacturing method thereof. This LCD device achieves such improvementsby arranging a common electrode on the same layer as a pixel electrodeand a layer different from the pixel electrode.

Additional features and advantages of the embodiments will be set forthin the description which follows, and in part will be apparent from thedescription, or may be learned by practice of the embodiments. Theadvantages of the embodiments will be realized and attained by thestructure particularly pointed out in the written description and claimshereof as well as the appended drawings.

According to one general aspect of the present embodiment, an LCD deviceincludes: a gate line disposed along a first direction; a data linecrossing the gate line along a second direction; a thin film transistordisposed on the gate line and connected to the gate line and the dataline; a first common electrode disposed on the same layer as the gateline and including first and second horizontal electrode bars and aplurality of first vertical common electrode bars; a second commonelectrode disposed on a layer different from the first common electrodeand including a third horizontal common electrode bar and a plurality ofsecond vertical common electrode bars; and a pixel electrode disposed onthe same layer as the second common electrode and including a horizontalpixel electrode bar and a plurality of vertical pixel electrode bars,wherein the second common electrode is connected to the first commonelectrode and disposed to overlap the first common electrode.

An LCD device manufacturing method according to another aspect of thepresent embodiment includes: forming a gate line and a first commonelectrode, which includes first and second horizontal common electrodebars and a plurality of first vertical common electrode bars, on asubstrate; forming an gate insulation film on the substrate includingthe gate line; forming a semiconductor layer on the gate insulation filmopposite to the gate line; forming a data line and source/drainelectrodes on the substrate including the semiconductor layer; forming apassivation film, which includes a contact hole exposing the secondhorizontal common electrode bar, on the substrate including the dataline; and forming a pixel electrode, which includes a horizontal pixelelectrode bar and a plurality of vertical pixel electrode bars, and asecond common electrode which includes a third horizontal commonelectrode bar and a plurality of second vertical common electrode bars,on the passivation film, wherein the third horizontal common electrodebar is connected to the second horizontal common electrode bar throughthe contact hole.

Other systems, methods, features and advantages will be, or will become,apparent to one with skill in the art upon examination of the followingfigures and detailed description. It is intended that all suchadditional systems, methods, features and advantages be included withinthis description, be within the scope of the invention, and be protectedby the following claims. Nothing in this section should be taken as alimitation on those claims. Further aspects and advantages are discussedbelow in conjunction with the embodiments. It is to be understood thatboth the foregoing general description and the following detaileddescription of the present disclosure are exemplary and explanatory andare intended to provide further explanation of the disclosure asclaimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the embodiments and are incorporated in and constitutea part of this application, illustrate embodiment(s) of the inventionand together with the description serve to explain the disclosure. Inthe drawings:

FIG. 1 is a view showing an LCD device of the 1-metal-1-ITOconfiguration according to the related art;

FIG. 2 is a graphic diagram showing light transmittance in an LCD deviceof FIG. 1 manufactured with a mask misalignment;

FIG. 3A is a view showing an LCD device of the 2-ITO configurationaccording to the related art;

FIG. 3B is a graphic diagram showing light transmittance in by an LCDdevice of the 2-ITO configuration shown in FIG. 3A;

FIG. 4A is a view showing an LCD device of the 2MoTi configurationaccording to the related art;

FIG. 4B is a graphic diagram showing light transmittance in an LCDdevice of the 2Moti configuration shown in FIG. 4A

FIG. 5 is a plane view showing an LCD device of an IPS mode according toan embodiment of the present disclosure;

FIG. 6 is a cross-sectional view showing sectional surfaces taken alonglines A-A′, B-B′, and C-C′ in the LCD device of an IPS mode shown inFIG. 5;

FIG. 7 is a graphic diagram showing light transmittance in the LCDdevice of an IPS mode shown in FIG. 5; and

FIGS. 8A through 8D are cross-sectional views explaining a method ofmanufacturing the LCD device of an IPS mode according to an embodimentof the present disclosure.

FIG. 9 is a plane view showing an LCD device of an IPS mode according toanother embodiment of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments of the presentdisclosure, examples of which are illustrated in the accompanyingdrawings. These embodiments introduced hereinafter are provided asexamples in order to convey their spirits to the ordinary skilled personin the art. Therefore, these embodiments might be embodied in adifferent shape, so are not limited to these embodiments described here.Also, the size and thickness of the device might be expressed to beexaggerated for the sake of convenience in the drawings. Whereverpossible, the same reference numbers will be used throughout thisdisclosure including the drawings to refer to the same or like parts.

FIG. 5 is a plane view showing an LCD device of an IPS mode according toan embodiment of the present disclosure. FIG. 6 is a cross-sectionalview showing sectional surfaces taken along lines A-A′, B-B′, and C-C′in the LCD device of an IPS mode shown in FIG. 5. Although FIG. 5 showsonly a unit pixel region for the convenience of explanation, theembodiment of the present disclosure is not limited to this. In otherwords, the embodiment of the present disclosure must be applied to anLCD device in which the unit pixel region shown in FIG is arranged in amatrix.

Referring to FIGS. 5 and 6, a substrate 11 includes a gate line 13 and afirst common electrode 20. The gate line 13 may be disposed along afirst direction (for example, a horizontal direction). The gate line 13included in the LCD device of the present embodiment can be used as agate electrode which is one of the components of a thin film transistor.In other words, the thin film transistor can be formed on the gate line13.

The first common electrode 20 includes first and second horizontalcommon electrode bars 21 and 23 arranged to be separated from each otherin the first direction, and a plurality of first vertical commonelectrode bars 25 a to 25 e extended between the first and secondhorizontal common electrode bars 21 and 23 in a second direction (forexample, a vertical direction). The first horizontal common electrodebar 21 is disposed adjacent to the gate line 13. Meanwhile, the secondhorizontal common electrode bar 23 is disposed adjacent to a precedinggate line which is positioned in a preceding pixel region ahead of thegate line 13.

The first vertical common electrode bars 25 a to 25 e may extend fromthe first horizontal common electrode bar 21 to the second horizontalcommon electrode bar 23. In other words, the first vertical commonelectrode bars 25 a to 25 e connected between the first and secondhorizontal common electrode bars 21 and 23 are arranged along the seconddirection (i.e., the vertical direction). The first vertical commonelectrode bars 25 a to 25 e can also have a crooked (or curved) shape.Furthermore, the first vertical common electrode bars 25 a to 25 e canintegrally be formed with the first and second horizontal commonelectrode bars 21 and 23.

The gate line 13 and the first common electrode 20 can include either asingle layer formed of one material selected from a group which consistsof cooper (Cu), aluminum (Al), Molybdenum (Mo), tungsten (W), titanium(Ti), a cooper alloy, an aluminum alloy, a molybdenum alloy, a tungstenalloy, and a titanium alloy, or a stacked layer formed of at least twoselected from the above group.

A gate insulation film 27 is disposed on the entire surface of thesubstrate with the gate line 13 and the first common electrode 20. Thegate insulation film 27 may be formed of an organic material or aninorganic material.

A semiconductor layer 29 including an active layer and an ohmic contactlayer is formed on the gate insulation film 27 opposite to the gate line13. The active layer may be formed of silicon. The ohmic contact layercan be formed by doping an impurity into silicon.

A data line 35 and source/drain electrodes 31 and 33 are arranged on thesemiconductor layer 29. The data line 35 is disposed crossing the gateline 13. The source electrode 31 is connected to the data line 35 in aunified manner. The drain electrode 33 is disposed separated from thesource electrode 31. The data line 35 and the source/drain electrodes 31and 33 can be formed of either the same material as the gate line 13 ora material different from the gate line 13. More specifically, the dataline 35 and the source/drain electrodes 31 and 33 can include either asingle layer formed of one material selected from a group which consistsof cooper (Cu), aluminum (Al), Molybdenum (Mo), tungsten (W), titanium(Ti), a cooper alloy, an aluminum alloy, a molybdenum alloy, a tungstenalloy, and a titanium alloy, or a stacked layer formed of at least twoselected from the above group. Furthermore, the data line 35 has acrooked (or curved) shape in order to be separated at a fixed distancefrom vertical pixel electrode bars and second vertical common electrodebars of the second common electrode described below. This is due to thefact that the vertical pixel electrode bars and the second verticalcommon electrode bars form a crooked shape (or a curved shape).

In this manner, a thin film transistor 30 including the gate line 13,the gate insulation film 27, the semiconductor layer 29, and thesource/drain electrodes 31 and 33 can be formed. This thin filmtransistor 30 is connected to the gate line 13 and the data line 35.

A passivation (or protective) film 37 is formed on the substrate 11which includes the thin film transistor 30. The passivation film 37includes a contact hole 41 exposing the drain electrode 33, and a secondcontact hole 43 exposing the second horizontal common electrode bar 23of the first common electrode 20.

A pixel electrode 50 and a second common electrode 60 are arranged onthe passivation film 37. The pixel electrode 50 and the second commonelectrode 60 can be formed of the same material as each other and can bearranged on the same layer.

The pixel electrode 50 includes a horizontal electrode bar 51 and aplurality of vertical pixel electrode bars 53 a to 53 d extending fromthe horizontal electrode bar 51.

The second common electrode 60 includes a third horizontal commonelectrode bar 61 and a plurality of second vertical common electrodebars 63 a to 63 c extending from the third horizontal common electrodebar 61. The second vertical common electrode bars 63 a to 63 c arearranged to overlap the first vertical common electrode bars 25 b to 25d except the first vertical common electrode bars 25 a and 25 epositioned at the outermost sides. The second vertical common electrodebars 63 a to 63 c are either equal to or wider than the respective firstvertical common electrode bars 25 b to 25 d. It is preferable for thesecond vertical common electrode bars 63 a to 63 c to have a width widerthan that of the respective first vertical common electrode bars 25 b to25 d.

If a mask is used in the formation of the first common electrode 20, themask can be misaligned. In this case, the distances between the firstvertical common electrode bars 25 b to 25 d of the first commonelectrode 20 and the vertical pixel electrode bars 53 a to 53 d of thepixel electrode 50 are different from each other. Also, the firstvertical common electrode bars 25 b to 25 d of the first commonelectrode 20 are not overlapped by the second vertical common electrodebars 63 a to 63 c of the second common electrode 60 but are separatedfrom them. As such, light does not penetrate through the separatedregions (or gaps) between the first vertical common electrode bars 25 bto 25 d of the first common electrode 20 and the second vertical commonelectrode bars 63 a to 63 c of the second common electrode 60, due tothe opacity of the first vertical common electrode bars 25 b to 25 d.Light penetrating through the separated regions (or the gaps) is alsonot affected by an equivalent electric field formed on the firstvertical common electrode bars 25 b to 25 d. In this case, as theseparated regions have the same size respectively, distances between theseparated region are also identical with each other. Therefore,transmission regions adjacent to each of the vertical pixel electrodebars 53 a to 53 d have the same light transmittance as each other.Hereinafter, the transmission regions are regions except the separatedregions in each pixel. As a result, the transmittance is not lowered.

In addition, the opaque first vertical common electrode bars 25 b to 25d of the first common electrode 20 are arranged not to overlap any ofthe second vertical common electrode bars 63 a to 63 c. Accordingly, thecontrast ratio of the unit pixel region can be improved.

The pixel electrode 50 and the second common electrode 60 can be formedof a transparent conductive material such as ITO (indium tin oxide), IZO(indium zinc oxide), and ITZO (indium tin-zinc oxide). The pixelelectrode 50 may be electrically connected to the drain electrode 33 ofthe thin film transistor 30 through the first contact hole 41. Thesecond common electrode 60 may be electrically connected to the firstcommon electrode 20 through the second contact hole 43. In other words,the third horizontal common electrode bar 61 of the second commonelectrode 60 can be electrically connected to the second horizontalcommon electrode bar 23 of the first common electrode 20.

The outermost vertical pixel electrode bars 53 a and 53 d of the pixelelectrode 50 and the outermost first vertical common electrode bars 25 aand 25 e can configure a storage capacitor together with the passivationfilm 37 and the gate insulation film 27 which are interposed betweenthem. Also, the horizontal pixel electrode bar 51 of the pixel electrode50 and the first horizontal common electrode bar 21 of the first commonelectrode 20 can configure another storage capacitor together with thepassivation film 37 and the gate insulation film 27 which are interposedbetween them. As such, the storage capacitor is formed between the firsthorizontal common electrode bar 21 and the horizontal pixel electrodebar 51 and between the outermost first vertical common electrode bars 25a and 25 e and the outermost vertical pixel electrode bars 53 a and 53d. Therefore, the capacitance of the storage capacitor can becomelarger.

The third horizontal common electrode bar 61 and the horizontal pixelelectrode bar 51 can be arranged parallel to the gate line 13. Thevertical pixel electrode bars 53 a to 53 d and the second verticalcommon electrode bars 63 a to 63 c can be arranged parallel to the dataline 35. Also, the vertical pixel electrode bars 53 a to 53 d and thesecond vertical common electrode bars 63 a to 63 c can have a crooked(curved) shape. The vertical pixel electrode bars 53 a to 53 d arealternately arranged with the second vertical common electrode bars 63 ato 63 c.

In this way, the first and second vertical common electrode bars 25 a to25 e and 63 a to 63 c are arranged on the different layers, and thevertical pixel electrode bars 53 b and 53 c are arranged between thesecond vertical common electrode bars 63 a to 63 c. As such, IPSelectric fields (or horizontal electric fields) can be induced betweenthe vertical pixel electrode bars 53 b and 53 c and the first verticalcommon electrode bars 25 b to 25 d and between the vertical pixelelectrode bars 53 b and 53 c and the second vertical common electrodebars 63 a to 63 c.

In addition to this, since the first vertical common electrode bars 25 bto 25 d formed of an opaque metal material shield light, the lighttransmittance in the openings (or gaps) between the first verticalcommon electrode bars 25 b to 25 d and the vertical pixel electrode bars53 b and 53 c become higher, as shown in FIG. 7. Accordingly, the LCDdevice of the present embodiment can have an improved contrast ratiocompared to those of the 1-matal-1-ITO and 2-ITO configurationsaccording to the related art.

Furthermore, the first vertical common electrode bars 25 b to 25 d andthe second vertical common electrode bars 63 a to 63 c are arranged tooverlap each other. As such, the openings between the vertical pixelelectrode bars 52 b and 53 c and one of the first and second verticalcommon electrode bars 25 b to 25 d and 63 a to 63 c may be equal to oneanother in width, even though the mask is misaligned during theformation of the first common electrode 20. Therefore, the LCD device ofthe present embodiment can greatly improve the light transmittance incomparison with those of the 1-matal-1-ITO and 2-ITO configurationsaccording to the related art.

Consequently, the LCD device of the present embodiment may have a1-metal-2-ITO configuration which includes the first common electrode 20formed of a metal, the pixel electrode 50 of the transparent conductivefilm, and the second common electrode 60 of the transparent conductivefilm disposed on the same layer as the pixel electrode 50. It is evidentthat the 1-metal-2-ITO configuration of the present embodiment can havesuperior light-transmittance compared to the 1-metal-1-ITO and 2MoTiconfigurations of the related art, and a contrast ratio higher thanthose of the 1-metal-1-ITO and 2-ITO configurations according to therelated art, as described in the following table 1.

TABLE 1 1-Metal-1-ITO 2-ITO 2MoTi 1-Metal-2-ITO Transmittance 400.3439.2 407.4 428.3 Contrast Ratio 1053 1046 1164 1086

Also, DC (direct current) residual image and static electricitycharacteristics are measured. These measurements show that the1-metal-2-ITO configuration of the present embodiment is superior to therelated art configurations.

FIGS. 8A through 8D are cross-sectional views explaining a method ofmanufacturing the LCD device of an IPS mode according to an embodimentof the present disclosure. The method of manufacturing the LCD device ofan IPS mode according to the present embodiment will now be explainedreferring to FIGS. 5 and 8A to 8D.

As shown in FIG. 8A, a gate line 13 and a first common electrode 20 areformed on a substrate 11 through a process of forming a first metal filmon the substrate 11 and patterning the first metal film. The first metalfilm can include either a single layer formed of one material selectedfrom a group which consists of cooper (Cu), aluminum (Al), Molybdenum(Mo), tungsten (W), titanium (Ti), a cooper alloy, an aluminum alloy, amolybdenum alloy, a tungsten alloy, and a titanium alloy, or a stackedlayer formed of at least two selected from the above group. The gateline 13 and the first common electrode 20 may be formed within a pixelregion.

The gate line 13 functions as a gate electrode. As such, a thin filmtransistor, which will be formed thereafter, can be disposed on the gateline 13. The gate line 13 may be formed along a first direction (forexample, a horizontal direction).

The first common electrode 20 includes first and second horizontalcommon electrode bars 21 and 23 separated from each other, and aplurality of first vertical common electrode bars 25 a to 25 e extendedbetween the first and second horizontal common electrode bars 21 and 23in such a manner as to be unified with the horizontal common electrodebars 21 and 23. The first horizontal common electrode bar 21 is disposedadjacent to a respective gate line 13. Meanwhile, the second horizontalcommon electrode bar 23 is disposed adjacent to a preceding gate linewhich is positioned in a preceding pixel region ahead of the respectivegate line 13. The first vertical common electrode bars 25 a to 25 ebetween the first and second horizontal common electrode bars 21 and 23can be formed in a unified manner (i.e., of a single body) with thefirst and second horizontal common electrode bars 21 and 23. The firstvertical common electrode bars 25 a to 25 e also can have a crooked (orcurved) shape. The first and second horizontal common electrode bars 21and 23 are formed parallel to the gate line 13. The first verticalcommon electrode bars 25 a to 25 e are formed extending along a seconddirection (i.e., a vertical direction) perpendicular to the gate line13.

On the entire surface of the substrate 11 including the gate line 13, agate insulation film 27 is formed of either an organic material or aninorganic material.

A semiconductor layer 29 including an active layer and an ohmic contactlayer is formed on the gate insulation film 27 by forming and thenpatterning an active film and an ohmic contact film on the gateinsulation film 27, as shown in FIG. 8B. The active layer may be formedof silicon. The ohmic contact layer can be formed by doping an impurityinto silicon. The semiconductor layer 20 can be formed on the gate line13.

Referring to FIG. 8C, a data line 35 and source/drain electrodes 31 and33 are formed on the substrate 11 with the semiconductor layer 29,through a process of forming and patterning a second metal film on thesubstrate. The second metal film can include either a single layerformed of one material selected from a group which consists of cooper(Cu), aluminum (Al), Molybdenum (Mo), tungsten (W), titanium (Ti), acooper alloy, an aluminum alloy, a molybdenum alloy, a tungsten alloy,and a titanium alloy, or a stacked layer formed of at least two selectedfrom the above group.

The data line 35 is disposed crossing the gate line 13. In other words,the data line 35 is formed along the second direction (i.e., thevertical direction). At the same time, the outermost first verticalcommon electrode bars 25 a and 25 e of the first vertical commonelectrode bars 25 a to 25 e can be formed adjacent to the data line 35within the pixel region. The data line 35 can be bent parallel to thefirst vertical common electrode bars 25 a to 25 e. In other words, thedata line 35 may be formed parallel to the first vertical commonelectrode bars 25 a to 25 e. The source electrode 31 is formed in such amanner as to be unified with the data line 35. The drain electrode 33 isdisposed separately from the source electrode 31.

In this way, the pixel region is defined by the crossing of the dataline 35 and the gate line 13. A thin film transistor 30 including thegate line 13, the gate insulation film 27, the semiconductor layer 29,and the source/drain electrodes 31 and 33 can then be formed.

Then, a passivation (or protective) film 37 is formed, by either coatingan organic material or depositing an inorganic mater, on the substrate11 with the data line 35, as shown in FIG. 8C. The passivation film ispatterned to form a first contact hole 41 exposing the drain electrode33 and a second contact hole 43 exposing the second horizontal commonelectrode bar 23.

As shown in FIG. 8D, a pixel electrode 50 and a second common electrode60 are provided on the passivation film 37 by forming and patterning atransparent conductive film on the passivation film 37. The transparentconductive film can be formed of any one of ITO, IZO, and ITZO.

The pixel electrode 50 includes a horizontal electrode bar 51 and aplurality of vertical pixel electrode bars 53 a to 53 d extending fromthe horizontal electrode bar 51. The vertical pixel electrode bars 53 ato 53 d are formed to be unified with the horizontal pixel electrode bar51. The horizontal pixel electrode bar 51 is electrically connected tothe drain electrode 33 of the thin film transistor 30 through the firstcontact hole 41.

The horizontal electrode bar 51 is formed to overlap the firsthorizontal common electrode bar 21 adjacent to the gate line 21. Assuch, the horizontal electrode bar 51 and the first horizontal commonelectrode bar 21 can form a storage capacitor together with thepassivation film 37 and the gate insulation film 27 interposed betweenthem.

The outermost vertical pixel electrode bars 53 a and 53 d of thevertical pixel electrode bars 53 a to 53 d also are formed to overlapthe outermost first vertical common electrode bars 25 a and 25 e of thefirst vertical common electrode bars 25 a to 25 e within the pixelregion. Accordingly, the outermost vertical pixel electrode bars 53 aand 53 d and the outermost first vertical common electrode bars 25 a and25 e can form another storage capacitor together with the passivationfilm 37 and the gate insulation film 27 interposed between them.

The second common electrode 60 includes a third horizontal commonelectrode bar 61 and a plurality of second vertical common electrodebars 63 a to 63 c extending from the third horizontal common electrodebar 61. The plural second vertical common electrode bars 63 a to 63 care formed to be unified with the third horizontal common electrode bar61. The third horizontal common electrode bar 61 is electricallyconnected to the second horizontal common electrode bar 23 through thesecond contact hole 43.

The second vertical common electrode bars 63 a to 63 c can alternatelybe formed with the vertical pixel electrode bars 53 a to 53 d. Also, thesecond vertical common electrode bars 63 a to 63 c are arranged tooverlap the respective first vertical common electrode bars 25 b to 25d. To this end, the second vertical common electrode bar 63 a to 63 care either equal to or wider than the respective first vertical commonelectrode bars 25 b to 25 d. In other words, the second vertical commonelectrode bars 63 a to 63 c may be formed in a width great enough tocover the respective first vertical common electrode bars 25 b to 25 d.

The second vertical common electrode bars 63 a to 63 c and the verticalpixel electrode bars 53 a to 53 d can be formed parallel to the dataline 35. As such, the second vertical common electrode bars 63 a to 63 cand the vertical pixel electrode bars 53 a to 53 d may have curvedshapes.

In this matter, the LCD device of the present embodiment forms the firstand second common electrodes 20 and 60, which are electrically connectedto each other, on different layers. The LCD device also forms the pixelelectrode 50 on the same layer as the second common electrode 60.Furthermore, the LCD device forms the first vertical common electrodebars 25 b to 25 d of the first common electrode 20 and the secondvertical common electrode bars 63 a to 63 c of the second commonelectrode 60 to overlap each other. As such, the openings between thevertical pixel electrode bars 53 b and 53 c of the pixel electrode 50and one group of the first vertical common electrode bars 25 b to 25 dof the first common electrodes 20 and the second vertical commonelectrode bars 63 a to 63 c of the second common electrode 60 may beequal to one another in width, even though the first common electrode 20is shifted toward any one side due to mis-alignment of the mask.Accordingly, the light transmittances in the openings are all the same.As a result, the LCD device of the present embodiment can greatlyimprove the light transmittance.

In addition, since the opaque first common electrode 20 is formed tooverlap the second common electrode 60, it shields light. Therefore, thelight transmittance in the openings (or gaps) becomes higher.Accordingly, the LCD device of the present embodiment can improve thecontrast ratio.

On the other hand, the first common electrode 20 can be formed in astacked layer of at least two metal materials. For example, the firstcommon electrode 20 can be formed in a double layer of MoTi/Cu. In thiscase, the first common electrode 20 of the stacked layer causes stepcoverage in different layers formed on the first common electrode 20,thereby misaligning liquid crystal during a rubbing process. Therefore,a light leakage phenomenon is generated.

To address this matter, as shown in FIG. 9, a gate line 13 includesfirst and second layers 17 a and 17 b, and a first horizontal electrodebar 21, a second horizontal electrode bar 23 (refer to FIG. 5) and aplurality of first vertical common electrode bars 25 a to 25 e includethe first layer 17 a, respectively. For instance, the first layer 17 amay be formed of MoTi and the second layer 17 b may be formed of Cu. Thefirst and second layers 17 a and 17 b are formed on a substrate 11.Then, the second layer 17 b is removed to form the first horizontalelectrode bar 21, the second horizontal electrode bar 23 (refer to FIG.5) and the plurality of first vertical common electrode bars 25 a to 25e. Thus the first common electrode 20 is of a greatly reduced thickness.As such, the step coverage caused by the first common electrode 20 maybe minimized and the liquid crystal may be uniformly aligned.Accordingly, the light leakage phenomenon can be prevented.

As described above, the LCD device according to an embodiment of thepresent disclosure enables the openings between the pixel electrode barsof the pixel electrode and one of the first common electrode bars of thefirst common electrodes and the second common electrode bars of thesecond common electrode to be equal to one another in width, even thoughthe first common electrode is shifted toward one side during themisalignment of the mask. Therefore, the light transmittances in theopenings are all the same. As a result, the LCD device of the presentembodiment can greatly improve the light transmittance.

Also, since the opaque first common electrode is formed to overlap thesecond common electrode, it shields light, making the lighttransmittance in the openings (or gaps) higher. Accordingly, the LCDdevice of the present embodiment can improve the contrast ratio.

Although the present disclosure has been limitedly explained regardingonly the embodiments described above, it should be understood by theordinary skilled person in the art that the present disclosure is notlimited to these embodiments, but rather that various changes ormodifications thereof are possible without departing from the spirit ofthe present disclosure. Accordingly, the scope of the present disclosureshall be determined only by the appended claims and their equivalents.

What is claimed is:
 1. A liquid crystal display device comprising: agate line disposed along a first direction; a data line crossing thegate line along a second direction; a thin film transistor disposed onthe gate line and connected to the gate line and the data line; a firstcommon electrode disposed on the same layer as the gate line andincluding first and second horizontal electrode bars and a plurality offirst vertical common electrode bars extended between the first andsecond horizontal electrode bars, the first horizontal electrode bardisposed adjacent to the gate line; a second common electrode disposedon a layer different from the first common electrode and including athird horizontal common electrode bar and a plurality of second verticalcommon electrode bars; and a pixel electrode disposed on the same layeras the second common electrode and including a horizontal pixelelectrode bar and a plurality of vertical pixel electrode barsalternately arranged with the plurality of second vertical commonelectrode bars, wherein an entire region of the second horizontalelectrode bar of the first common electrode overlap the third horizontalelectrode bar of the second common electrode, wherein the thirdhorizontal electrode bar of the second common electrode and thehorizontal pixel electrode bar of the pixel electrode are disposed onthe same layer, wherein the outermost first vertical common electrodebars of the first common electrode overlap the corresponding outermostvertical pixel electrode bars of the pixel electrode, respectively toform a storage capacitor, and wherein the remaining first verticalcommon electrode bars of the first common electrode between theoutermost first vertical common electrode bars each entirely overlapwith each corresponding one of the second vertical common electrode barsof the second common electrode along a lengthwise direction of thesecond vertical common electrode bars.
 2. The liquid crystal displaydevice according to claim 1, wherein the second vertical commonelectrode bars are arranged to overlap the first vertical commonelectrode bars, respectively.
 3. The liquid crystal display deviceaccording to claim 2, wherein the second vertical common electrode barshave at least width larger than the respective first vertical commonelectrode bars.
 4. The liquid crystal display device according to claim1, wherein the third horizontal common electrode bar of the secondcommon electrode is connected to the second horizontal common electrodebar of the first common electrode.
 5. The liquid crystal display deviceaccording to claim 1, wherein the horizontal pixel electrode bar and thefirst horizontal common electrode bar overlap together with apassivation film and a gate insulation film interposed therebetween toform another storage capacitor.
 6. The liquid crystal display deviceaccording to claim 1, wherein the vertical pixel electrode bars and thefirst and second vertical common electrode bars have crooked (or curvedor bent) shapes.
 7. The liquid crystal display device according to claim1, wherein the gate line include first and second layers and the firstcommon electrode include the first layer.
 8. A method of manufacturing aliquid crystal display device, the method comprising: forming a gateline and a first common electrode, which includes first and secondhorizontal common electrode bars and a plurality of first verticalcommon electrode bars, on a substrate; forming an gate insulation filmon the substrate including the gate line; forming a semiconductor layeron the gate insulation film opposite to the gate line; forming a dataline and source/drain electrodes on the substrate including thesemiconductor layer; forming a passivation film, which includes acontact hole exposing the second horizontal common electrode bar, on thesubstrate including the data line; and forming a pixel electrode, whichincludes a horizontal pixel electrode bar and a plurality of verticalpixel electrode bars, and a second common electrode which includes athird horizontal common electrode bar and a plurality of second verticalcommon electrode bars alternately arranged with the plurality ofvertical pixel electrode bars, on the passivation film, wherein anentire region of the second horizontal electrode bar of the first commonelectrode overlap the third horizontal electrode bar of the secondcommon electrode, wherein the third horizontal electrode bar of thesecond common electrode and the horizontal pixel electrode bar of thepixel electrode are disposed on the same layer, wherein the outermostfirst vertical common electrode bars of the first common electrodeoverlap the corresponding outermost vertical pixel electrode bars of thepixel electrode, respectively to form a storage capacitor, and whereinthe remaining first vertical common electrode bars of the first commonelectrode between the outermost first vertical common electrode barseach entirely overlap with each corresponding one of the second verticalcommon electrode bars of the second common electrode along a lengthwisedirection of the second vertical common electrode bars.
 9. The methodaccording to claim 8, wherein the second common electrode is formed tooverlap the first common electrode.
 10. The method according to claim 8,wherein the second vertical common electrode bars are formed to overlapthe first vertical common electrode bars, respectively.
 11. The methodaccording to claim 10, wherein the second vertical common electrode barshave at least width larger than the respective first vertical commonelectrode bars.
 12. The method according to claim 8, wherein thehorizontal pixel electrode bar and the first horizontal common electrodebar overlap together with a passivation film and a gate insulation filminterposed therebetween to form another storage capacitor.
 13. Theliquid crystal display device according to claim 1, wherein the thirdhorizontal common electrode bar is connected to the second horizontalcommon electrode bar through a contact hole.
 14. The liquid crystaldisplay device according to claim 1, wherein openings between theplurality of vertical pixel electrode bars and one of the plurality offirst vertical common electrode bars and the plurality of secondvertical common electrode bars are equal to one another in width. 15.The method according to claim 8, wherein openings between the pluralityof vertical pixel electrode bars and one of the plurality of firstvertical common electrode bars and the plurality of second verticalcommon electrode bars are equal to one another in width.